rcu/kfree: Fix kfree_rcu_shrink_count() return value

joelagnel · paulmckrcu · commit 382690963518 · 2022-08-31T05:06:50.000-07:00
As per the comments in include/linux/shrinker.h, .count_objects callback
should return the number of freeable items, but if there are no objects
to free, SHRINK_EMPTY should be returned. The only time 0 is returned
should be when we are unable to determine the number of objects, or the
cache should be skipped for another reason.

Signed-off-by: Joel Fernandes (Google) &lt;joel@joelfernandes.org&gt;
Reviewed-by: Uladzislau Rezki (Sony) &lt;urezki@gmail.com&gt;
Signed-off-by: Paul E. McKenney &lt;paulmck@kernel.org&gt;
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
@@ -3372,7 +3372,7 @@ kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
 		atomic_set(&krcp->backoff_page_cache_fill, 1);
 	}
 
-	return count;
+	return count == 0 ? SHRINK_EMPTY : count;
 }
 
 static unsigned long

Original file line number	Diff line number	Diff line change
`@@ -3372,7 +3372,7 @@ kfree_rcu_shrink_count(struct shrinker shrink, struct shrink_control sc)`
`3372`	`3372`	`atomic_set(&krcp->backoff_page_cache_fill, 1);`
`3373`	`3373`	`}`
`3374`	`3374`
`3375`		`- return count;`
	`3375`	`+ return count == 0 ? SHRINK_EMPTY : count;`
`3376`	`3376`	`}`
`3377`	`3377`
`3378`	`3378`	`static unsigned long`